With the development of equipment for high precision, high reliability, long life, and deep space applications (Whelan et al., 2001; Zheng et al., 2013; Scheffer, 2016), there has been an increasing demand on the functionality, performance, integration density, and reliability of integrated circuits under constraints of equipment size and weight. This trend had led to the growing widespread application of bare dies. Therefore, it is crucial to not overlook evaluation of the quality and reliability of newly selected bare dies.

Through the known-good bare die (KGD) technique (Singh et al., 1997; Chen et al., 2022; Yoo and Meng, 2021), reliability tests such as functionality, performance, burn-in, and screening can ensure the quality and reliability of bare dies. The series standards that have been established include American JESD49 KGD (Procurement Standard for Semiconductor Die, 2020), Japanese EIAJ EDR-4703, and European ES59008 and IEC62258. The entire process from design verification to production process control and die screening assures the quality of bare dies.

To meet the equipment requirements for bare dies, it is necessary to conduct analysis of the selection management of bare dies based on system reliability. In order to respond to the demand for domestic bare dies and requirements for cost reduction and efficiency improvement, it is necessary to select products from mature, stable, and high-quality suppliers. Accordingly, in a typical application environment, the application’s reliability must be scientifically, effectively, and efficiently assessed to support bare die application. Based on the risk analysis of the reliability of bare dies, the physical properties, function, performance, environmental adaptability, and assembly adaptability are evaluated to verify whether bare die reliability and quality are suitable for application. The main processes to selective control are shown in Figure 1. Based on the requirements of the project, we selected a typical one and verified the effectiveness of the system analysis method. Considering both the typical application environment of the equipment and a reliability risk analysis of the application, we developed an evaluation plan for initial selected. This plan aimed to assess various aspects of the die, including physical characteristics, functionality, performance, environmental adaptability, and assembly compatibility in order to evaluate the suitability of the typical die.

To ensure that a selected bare die can be reliably applied in equipment, equipment requirements must be obtained for its typical application environment (Luo et al., 2001), functional performance, physical characteristics (Giannakaki and Katsanidis, 2023), and acceptable failure rate of bare dies. To meet the quality and reliability requirements of the equipment when choosing typical bare dies (Zieja et al., 2018; Kimmerle and Avenhaus, 2023), both the product supplier (Gheidar-Kheljani and Halat, 2024) and typical products should both be evaluated.

The reliability of components depends on the production process (Samokhin et al., 2019) and the management level of suppliers (Deviatko et al., 2024). To ensure the consistency, stability, and traceability of components, the capability assessment of suppliers (Allenbacher and Berg, 2023; Chen et al., 2020; Hulevich and Nalivaiko, 2021) includes design, raw material management, product process control (Hidayat et al., 2019; Mayrhofer et al., 2020; Sunadi et al., 2020), non-conforming product handling, stable supply (Spekman et al., 2001), and quality management (Kwilinski et al., 2023).

When selecting a typical die, products from well-known domestic manufacturers with established processes should be preferred. The manufacturer should be chosen from the top of the industry which reliably produces proven products.

After investigation, the typical power management bare die X43XXX was selected to apply in a specific device. The die had passed the qualification test as required and had stable supply. The evaluation of the selected typical products included microstructural characteristics, function and performance, environmental adaptability, and assembly adaptability.

Unreasonable structural design, mismatched material properties, or unstable process control may lead to a decline in the inherent reliability of components and increase potential safety hazards (Deviatko et al., 2024; Akbari et al., 2021). The physical properties of a bare die to be evaluated will affect its inherent reliability, operational reliability (Cheng et al., 2022; Feng et al., 2021), and service life (Alekseeva et al., 2023). It is necessary to analyze whether structural design, materials, and processes meet the requirements of the special application environment of the equipment. Structural analysis can determine the physical characteristics of potential operational reliability risks and eliminate them before the die is applied.

Microstructural characteristics (such as structure, process, and material) significantly influence the life expectancy and reliability of bare dies, necessitating thorough evaluation. Structural analysis is crucial in reliability assessment as it effectively identifies components with prohibited or restricted structures, as well as those posing quality risks, from being integrated into equipment. Structural analysis gives insights into the actual composition of electronic components and uncovers potential design weaknesses and manufacturing flaws, thereby ensuring compliance with established standards.

We decomposed the structural units of a typical bare die and identified key elements. The structural units and evaluation factors of the X43XXX die are listed in Table 1, including the die itself, bonding pads, and passivation layers. After decomposing the structural units, performance analysis and calculation of these units along with their constituent materials must be conducted. Based on the structural evaluation criteria for the bare die, structural analysis tests were formulated. The structural analysis test items for the X43XXX structure are shown in Table 2.

Three samples were selected for structural analysis. First, their physical dimensions were measured and subject to internal visual inspection using a stereo microscope and a metallographic microscope. The dicing quality of bare die X43XXX was good, with no observed damage or cracks. The surface showed no signs of blistering, peeling, or erosion. The backside was a substrate layer, and there were no metalized coatings on its surface. The passivation layer integrity of the die was qualified.

After embedding the bare die sample and performing cross-section inspections, a scanning electron microscope (SEM) and energy-dispersive spectrometer were utilized to analyze the structure and materials of the dare die. This revealed that the die featured a layered architecture encompassing surface passivation layers, internal multilayer metallization, interlayer bare dielectrics, and a bottom substrate layer. Further analysis indicated that the die’s substrate was composed of silicon (Si), with aluminum (Al) as the primary constituent in its metallization layers. The thickness of the topmost metallization layer was measured to be approximately 5.5 μm. The intermediate bare dielectric layers were found to primarily consist of carbon (C), oxygen (O), aluminum (Al), and silicon (Si). Additionally, the vias within the die were predominantly composed of carbon (C), oxygen (O), aluminum (Al), tungsten (W), and titanium (Ti).

By examining the die using a metallographic and a scanning electron microscope, it was observed that the bonding pad surface in the bonding area was smooth and continuous, with no signs of peeling, flaking, or bulging. It can be concluded from the structure, raw materials, and process design that the bare die had a reasonable structural design and contained no prohibited or restricted processes or materials. Therefore, this die met the requirements for encapsulation.

Based on the demand for high reliability, high performance, low cost, and short equipment cycle, the application of bare dies has become a new focus. Based on the selection control and reliability risk analysis of bare die applications, a reliability evaluation plan was needed before using a bare die for the first time. The evaluation tests assessed the functions, performance, reliability, and environmental adaptability of the dies, ensuring quality control when selecting a bare die for equipment. Before installing and applying bare dies on equipment, it is essential to implement quality control over their design and manufacturing processes to ensure inherent reliability. A first-time application should be combined with typical equipment for reliability evaluation. After additional selection and other quality assurance measures, trial applications can be conducted. Post-installation, the equipment will undergo environmental testing. During this process, further analysis will be required to understand the degradation of bare die packaging.